It has long been recognized that, in certain systems for the handling of fluids, there is a need for a valve in a flow line which allows a fluid to flow in one direction but prevents the fluid from flowing in the opposite direction. Such valves are generally referred to as check valves.
One form of check valve is the ball-and-socket check valve. The socket typically has an opening. The ball, which is larger than the opening, is fitted to the socket adjacent the opening and in contact with the fluid. When the fluid forces the ball away from the socket, the fluid flows in one direction through the opening. However, when the fluid forces the ball against the socket, the ball blocks the opening and substantially prevents the fluid from flowing in the opposite direction through the opening.
Unfortunately, many check valves do not completely prevent fluid from flowing in the opposite direction. For example, when the ball of the ball-and-socket check valve is forced against the socket, it may not perfectly seal the opening, permitting a significant flow of fluid in the opposite direction. This flow in the opposite direction is called backflow. Thus, these check valves are suitable only when a slight or moderate amount of backflow is acceptable .
There is frequently a need for a check valve that substantially eliminates backflow. For example, in the medical arts, patients frequently require intravenous administration of two therapeutic solutions simultaneously. Each solution is contained in a separate bag or bottle which is hung from a stand and connected to the patient by a tube. The tubes from the bags are typically joined at a Y connector and then channeled to the patient via a common tube terminating in a single needle.
In order to accurately administer these therapeutic solutions to the patient, it is important that the solutions only flow from their respective bags to the patient. However, in certain circumstances, for example, when one bag is hung higher than the other and the common tube is clamped shut, the solution in one bag may flow through the Y connector into the other bag. A check valve which effectively eliminates any backflow through the tubes leading from the bags would be extremely beneficial.